HYDRAULIC JACK HAMMER, FOR EXAMPLE FOR MARINE SAMPLING

Abstract: A hydraulic, especially a hydrostatic impact device, for example for marine sampling or pile driving, comprises a low pressure reservoir (33) which is completely or partially filled with air or other gas under, for example, atmospheric pressure, and a piston cylinder (34, 35, 49), where the space (35) in the piston cylinder below the piston (10) is openly connected with the low pressure reservoir (33). The impact device's lifting stroke is activated by the opening of a filling valve (6, 71) to the top (34) of the piston from a fluid reservoir (32) at higher pressure than the low pressure reservoir, and the drop stroke is activated by the opening of a drain valve (52a-b) and the draining of fluid from the top of the piston to the low pressure reservoir while at the same time the filling valve closes and vice versa. Between the piston cylinder and, for example, a sampler tube (64, 65) there is provided a so-called jump slide valve (39, 40) which can convert the drop hammer's kinetic energy into potential energy for the entire impact device. The impact device can thereby continue the drop hammer's upwardly directed movement after the completion of the cylinder's lifting stroke.

Description: HYDRAULIC JACK HAMMER, FOR EXAMPLE FOR MARINE SAMPLING. The invention concerns a hydraulic, especially a hydrostatic impact device, for example for marine sampling or for pile driving, according to the introduction to claim 1. The impact device according to the invention is used in order to drive a sampler tube down into the sedimentary layers on the seabed, the tube thus being more or less filled with samples of the sediments, which can then be pulled up to the surface together with the sampler. There are a number of versions of samplers of this kind in the prior art, of which two main types are most common. The simplest of these main types, the gravitation sampler, is based on the principle that weights are placed around an extension of the sampler tube, and that a device causes the weights with the sampler tube to fall freely from a height of 10-15 m above the seabed. There are several varieties of gravitation samplers, of which one group is the so-called piston corer which is characterized in that a piston is provided inside the actual sampler tube. The piston is connected to a surface vessel by a wire or the like, and this wire holds the piston approximately steady on a level with the seabed, while the weights drive the sampler tube closely past the piston and down into the sediments. In this way there is obtained under the piston a suction effect which improves the ratio between the tube's depth of penetration and the length of the sample. The advantage of the gravitation samplers is that they are relatively simple to operate provided they are not too heavy or the sampler tube is very long. However, depth of penetration and sample length are limited, especially when the sediments are relatively hard. Another problem has been the unfavourable weight distribution with the weight on top of the long tube, thus making it difficult to make the sampler hit the seabed vertically after the free fall. The second main type of marine sampler, the so-called "vibrocorer", is based on the principle that the sampler tube is located on a support frame which is lowered down to the desired position on the seabed, whereupon a mass which is placed on top of the sampler tube is caused to vibrate by means of an electrical or hydraulic motor. The vibrocorers have proved to be much more suitable than the gravitation samplers in hard sediments, but correspondingly uncompetitive in soft sediments where very long samples are desirable. The disadvantages with the vibrocorers have been that the support frame becomes large, heavy and unwieldy when it has to be adapted to long sampler tubes. Moreover the energy transfer from the surface vessel to the electrical or hydraulic vibration motor becomes problematic at great depths. Norwegian PCT application PCT/NO92/00078 deals with a sampler based on a hydrostatically operated drop hammer. In this case it is not necessary to transfer energy from a surface vessel down to the impact motor in the sampler, the impact motor deriving its energy on site from the potential energy in the pressure difference between surrounding water masses and a submerged reservoir with air or other gas under low pressure. One problem with the sampler according to PCT/NO92/00078 has been how to utilize the double-acting effect which has been aimed at, viz. that both the drop stroke and the recoil of the lifting force should contribute to the penetration. In practice it has been necessary to choose between narrow inlet openings which are unsatisfactory in dealing with the lifting recoil effect, or powerfully upwardly directed impacts on the sample at the end of the lifting stroke due to high velocity. Upwardly directed impacts of this kind spoil the quality of the sample and increase the wear on the sampler. This problem is solved according to the present invention by providing between the piston cylinder and the sampler tube, pile or other tool, a jump slide valve which between two extreme positions permits free axial movement of the impact device relative to a sampler tube, a pile or another tool, thus enabling the entire impact device to continue the drop hammer's upwardly directed movement after the completion of the cylinder's lifting stroke, until the upwardly directed kinetic energy is exhausted and a drop higher than the lifting cylinder's stroke length can begin. In this manner the following advantages are obtained: Large flow cross sections can be employed in the filling valve, which provides substantial lifting force and corresponding penetration force in the form of recoil effect. In addition to efficient utilization of the lifting force, the energy in the drop is also substantially increased. The problem with an upwardly directed impact is eliminated, resulting in improved sample quality. The invention according to the present application employs, as in PCT/N092/- 00078, an impact motor consisting of a piston cylinder with an attached stroke valve mechanism which automatically opens the filling valve when the piston reaches its top position, and which moreover automatically closes the filling valve and simultaneously opens the drain valve when the piston reaches its bottom position. A problem with the designs in PCT/NO92/00078, however, has been that at relatively great depths, the external water pressure influences the piston rod below the opening in the bottom of the piston cylinder in such a manner that the piston is pressed into its top position, thereupon activating the inlet valve and starting the impact device regardless of whether the sampler has reached the bottom or not. In order to avoid this problem a separate main inlet valve has been used which is kept closed until being activated on the bottom by a more or less complicated mechanism, e.g. in the form of a cable release with a weight and a spring which return the valve to the open position when the cable is relieved of the influence of the weight. In practice this entails certain handling complications which efforts have to be made to avoid. In relation to a design of the present invention, these problems are solved by having a piston rod consisting of an upper section above the piston and a lower section below the piston, the upper section extending in a tight opening through the top of the cylinder to the high pressure reservoir, and the lower section extending in a tight opening through the bottom of the cylinder to an area, e.g. a secondary cylinder, where it is exposed to the pressure in the surrounding liquid, the openings through the top and bottom of the cylinder respectively having approximately the same cross section, and the surrounding liquid possibly being permitted access to the high pressure reservoir and the secondary cylinder, with the result that the axial components of the pressure forces influencing the piston rod above the top of the cylinder and below the bottom of the cylinder respectively neutralize each other. The result is thereby achieved that the hydrostatic impact motor only works when the weight of the sampler's falling parts presses the cylinder downwards in relation to the piston until the piston reaches the top position in the cylinder. Furthermore the impact motor will only start when the impact device is lowered down to the bottom, thus causing the sampler tube or the pile and the piston rod connected therewith to be braked by the resistance in the sediments, while at the same time a separate main inlet valve can be omitted. Hydrostatic samplers, such as those described in PCT/NO92/00078 have such superior powers of penetration that the tube length required in order to utilize the capacity for penetration entails a problem with regard to handling on the surface vessel. The length of the tubes of the gravitation samplers and the vibrocorers are often so moderate that the entire length of sampler and tubes can be lifted in an ordinary A-frame which is often to be found at the stern section of the surface vessel. If this has not been possible, there have often been used - except in the case of vibrocorers - various types of "cribs" for sampler with tubes, where the cribs are hinged about a horizontal axis, can be pivoted between a horizontal and a vertical position either behind the stern or along the. rail of the vessel, and provide a rigid support for the sampler with tubes also in the horizontal position. These cribs are relatively heavy and unwieldy, especially in bad weather and if the tubes are extra long. This drawback is avoided in accordance with a further feature of the present invention by providing between the piston rod's lower part or an extension of this and the sampler tube, near the upper or lower part of the jump slide valve, a toggle joint which enables the longitudinal axis of the sampler tube, pile or tool to be deflected preferably by approximately 0 - 90 degrees or more relative to the piston rod's axis, and that the toggle joint comprises a locking mechanism which blocks this freedom of movement in one or more positions, a locked position making the longitudinal axes of the piston rod and the tool coincident or parallel. Further features and advantages of the present invention are presented in the independent claims 4-14. The invention will now be described in more detail with reference to the draw- ing. Fig. 1 is an arrangement of the impact device according to the invention completely assembled, in an entirely lifted position with the jump slide valve completely extended (on the left) and immediately after a drop (on the right) respectively. Fig. 2 illustrates the impact device in use as a marine, hydrostatic sampler. Fig. 3a illustrates an embodiment of details of the impact device according to the invention. Fig. 3b illustrates a detail in fig. 8 in another position. Fig. 4a illustrates an embodiment of the valve mechanism used in the impact device according to the invention with open filling valve and closed drain valve respectively. Fig. 4b illustrates an embodiment of the valve mechanism in fig. 4a, but with closed filling valve and open drain valve. Fig. 5a-b illustrates a second embodiment of the said valve mechanism. Fig. 6 illustrates a third embodiment of the said valve mechanism. Fig. 7 illustrates an embodiment of the blowout valve used in the impact device according to the invention. Fig. 8 illustrates an embodiment of a tip of the sampler tube used in the impact device according to the invention. In the description and claims the following definitions are used: "The drop" is the term used for the sum of the drop stroke in the piston (which comprises the drop hammer) and the return of the jump stroke (which comprises the entire impact device,). "The drop hammer" covers all parts which drop relative to the piston when the filling valve closes and the drain valve opens. In practice this will include most of the mass in the impact device together with any water which may have entered the low pressure chamber (33) during previous impacts, but, e.g. not the piston, piston rod, toggle joint and slide valve. "The drop stroke" is the term used for the relative movement between the drop hammer and the piston when the filling valve closes and the drain valve opens. "The filling valve" is the term used for that part of the stroke valve (6) which opens or closes between the high pressure reservoir (32) and the piston cylinder's upper chamber (34). "The jump stroke" is the term used for the relative movement between the impact device and the sampler tube which is permitted by the jump slide valve. "The jump slide valve" is the term used for the slide valve which is described in the main claim and which can convert the drop hammer's kinetic energy to potential energy for the entire impact device, by permitting further axial movement after the piston cylinder has completed its lifting stroke. "The high pressure reservoir" is the term used for the space (32) from which the filling valve obtains liquid under pressure in order to perform the lifting stroke. When the impact device is operated hydrostatically the high pressure reservoir is openly connected with the surrounding liquid and has approximately the same pressure as this. When the impact device is operated hydraulically the high pressure reservoir is closed to the surrounding liquid and instead connected to a high pressure pump directly or via a hose suited to this purpose. "The low pressure chamber, the low pressure reservoir" indicate a volume of air or other gas (33) which is connected to the drain valve and the piston's lower chamber (35) directly or via hoses and pipes suited to this purpose. When the impact device is operated, the low pressure chamber will be partially filled with liquid under rising pressure, until the pressure difference between the low pressure chamber (33,35) and the high pressure chamber (32) becomes too small to perform the lifting stroke. "The lifting stroke" is the term used for the hydraulic or hydrostatic piston motor movement which results from the opening of the filling valve and the closing of the drain valve, the drop hammer being raised and/or the piston being pressed downwards, depending on the resistance in the sediments. "Surrounding liquid" describes the medium, e.g. sea water or fresh water, into which the impact device is submerged and which supplies the hydrostatic pressure required for hydrostatic operation. "The impact device" (reference "1 etc.") comprises all parts of the present invention, with or without added weights, but not the sampler tube (65) with related parts such as the casing or plastic tube (64), sampler tube tip (90), core retaining device (93), etc. "The piston valve" comprises the sum of the filling valve and the drain valve, whether 5 these are assembled into a unit or not. The piston valve can also be called the stroke valve, since it controls the piston's stroke movement. "The drain valve" is the term used for that part (52) of the stroke valve (6) which opens or closes between the piston cylinder's upper chamber (34) and the 10 low pressure reservoir (33). "The blowout valve" is the term used for the valve which is described in claims 7 - 9. "The valve slide" is the term used for a slide in the stroke valve, and should not be 15 confused with, e.g., the jump slide valve or slide valves in the blowout valve. Even though this patent application is primarily concerned with a sampler for marine sediments, operated by hydrostatic energy from the pressure in sur- 20 rounding liquid, the patent also covers the application of the device according to the invention on shore, operated by the fluid pressure from a hydraulic pump. The fluid reservoir under high pressure described in the main claim should then be understood to be the fluid buffer which is confined between the inlet valve A ( and the hydraulic pump. 25 In addition to sampling the invention can also be used for pile driving or other activities where impact energy is implemented. Where the impact device according to the invention includes, e.g., a gas reser¬ voir, a piston cylinder, a valve or the like, it is obvious that there can be provided a number of one or more of these components. There can, e.g., be 30 envisaged a plurality of piston cylinders which are provided around a through- going slide valve in order thereby to save space. There can also be envisaged a plurality of low pressure chambers, e.g. in the form of empty standard gas bottles arranged around the piston cylinder in varying numbers according to requirements.

Claims: PATENT CLAIMS 1. A hydraulic, especially a hydrostatic impact device, for example for marine sampling or pile driving, comprising a low pressure reservoir (33) filled completely or partially with air or another gas or water vapour under low or moderate pressure, for example atmospheric pressure, and a piston cylinder (34,35,49), where the space (35) in the piston cylinder below the piston (10) is openly connected with the said low pressure reservoir (33), where the lifting stroke is activated by the opening of a filling valve (6,71) to the top (34) of the piston from a fluid reservoir (32) at higher pressure than the low pressure reservoir, and where the drop stroke is activated by the opening of a drain valve (52a-b) and the draining of fluid from the top of the piston to the low pressure reservoir while at the same time the filling valve closes and vice versa, c h a r a c t e r i z e d in that between the piston cylinder and a sampler tube (64,65), a pile or another tool there is provided a jump slide valve (39,40) which between two extreme positions (39a,39b) permits free axial movement of the impact device (1 etc.) relative to the sampler tube, the pile or the tool, thus enabling the entire impact device to continue the drop hammer's upwardly directed movement after the completion of the cylinder's (34) lifting stroke, until the upwardly directed kinetic energy is exhausted and a drop higher than the lifting cylinder's (34) stroke length can begin. 2. A hydraulic impact device according to claim 1, c h a r a c t e r i z e d in that the piston rod (8a-c,9) consists of an upper section (8) above the piston (10) and a lower section (9) below the piston (10), that the upper section (8) extends in a tight opening through the top (6) of the cylinder to the high pressure reservoir (32), that the lower section (9) extends in a tight opening through the bottom (13) of the cylinder to an area, e.g. a secondary cylinder (36), where it is exposed to pressure in the surrounding liquid, that the openings through the top and bottom of the cylinder respectively have approximately the same cross section, and that the surrounding liquid may be given access to the high pressure reservoir (32) and the secondary cylinder (36), with the result that the axial components of the pressure forces which influence the piston rod above the top of the cylinder and below the bottom of the cylinder respectively neutralize each other. 3. A hydraulic impact device according to claim 1 and/or 2, c h a r a c t e r i z e d in that between the piston rod's lower part (9) or an extension of this (11) and the sampler tube (64,65), near the upper or lower part of the jump slide valve (39,40), there is provided a toggle joint (38) which enables the longitudinal axis of the sampler tube, the pile or the tool to be deflected preferably by approximately 0 - 90 degrees or more relative to the piston rod's (9,11) axis, and that the toggle joint comprises a locking mechanism (42) which blocks this freedom of movement in one or more positions (fig. 3 a, fig. 3b), a locked position (fig. 3a) making the longitudinal axes of the piston rod and the tool coincident or parallel. 4. A hydraulic impact device according to claim 3, wherein there is provided a sampler tube comprising an outer tube (65) made of steel or the like, which gives the construction the required rigidity, and a casing or an inner tube of plastic or the like which is designed to contain the sediment sample and is withdrawn from the steel tube (65) together with the sample, c h a r a c t e r i z e d in that the toggle joint (fig. 3) in an open position permits the plastic tube (64a) to be withdrawn from or pushed in from the same end as the toggle joint, without having to dismantle the steel tube (65). 5. A hydraulic impact device according to one or more of the preceding claims, wherin there is provided a sampler tube comprising an outer tube made of steel or the like (65), which gives the sampler tube the required rigidity, and an inner casing or an inner tube of plastic or the like (64a,64), which is designed to contain the sediment sample and is withdrawn from the steel tube together with the sample, c h a r a c t e r i z e d in that at the top of the plastic tube there is located a valve (41) which closes when the sample has to be pulled out of the sediments and a suction effect is obtained above the sample, while at the same time there are provided openings (91) which are connected to the gap (fig. 8) between the plastic tube (64) and the steel tube (65) at the top (fig. 3) and the bottom (fig. 8) of the sampler tube, the pressure thus being equalized between the bottom of the sample (66,94) and the environment at the top of the sampler tube when the sampler tube with the sample (95) have to be withdrawn. 6. A hydraulic impact device according to claim 5, c h a r a c t e r i z e d in that in the bottom end of the sampler tube (fig. 8) there is mounted a sampler tube tip (90) attached to the steel tube (65), that there is mounted in the sampler tube tip a per se known core retaining device (93), that the said plastic tube (64) rests on the core retaining device, which in turn rests on the sampler tube tip (90), that there is mounted on or immediately above the core retaining device a packing (92) which seals the gap between the steel tube and the plastic tube, and that immediately above the said packing there are drilled openings (91) substantially radially through the sampler tube tip into the gap between the plastic tube and the steel tube, and that on the tip immediately above the said radial openings a moderate extension of the tip's outer diameter occurs, thus causing a gap to be created between the tip and the sediments outside the tip when the sampler tube is withdrawn from the sedi¬ ments, thus enabling water from the gap between the plastic tube and the steel tube to flow through the said radial openings (91) in the tip (90), on through the said gap between the sediments and the tip to the space (94) which is created under the core retaining device when the sample is withdrawn, thus approximately neutralizing the vacuum in the said space. 7. A hydraulic impact device according to claim 1, c h a r a c t e r i z e d in that between the low pressure reservoir (33) and the surrounding liquid there is a blowout valve (20, fig. 7a-b) which opens when the pressure of the surrounding liquid is lower than the low pressure reservoir, and closes when the pressure of the surrounding liquid is greater than the low pressure reservoir, and that the said blowout valve (20, fig. 7) comprises a float valve (81,83) arranged inside the slide (82) on a slide valve, the float valve (81,83,84) thus approximately closing off the passage of fluid from the environment through the hollow slide valve to the low pressure reservoir (33) as soon as the impact device is submerged in a fluid and the float (83,84) floats up, while the slide (82) in the slide valve (80,82,85), which provides a more complete seal and resists greater pressure difference, only closes when the pressure difference becomes sufficiently great to overcome the slide's weight, friction and any other resistance. 8. A hydraulic impact device according to claim 7, c h a r a c t e r i z e d in that the blowout valve (20, fig.7) lacks return mechanisms in both directions, with the result that it is only influenced by the float's (83,84) buoyancy and the fluid pressure, and the slide (82) - when the environmental pressure drops below the pressure of the low pressure reservoir and the pressure difference becomes sufficiently great to open it - remains open regardless of the reduction in the extent of the pressure difference, until the pressure difference changes direction. 9. A hydraulic impact device according to claim 7, c h a r a c t e r i z e d in that the float (83,84) in the said float valve (81,83) is in the form of a cup (83) with the opening facing downwards, the gas volume (84) confined in the cup giving the float the necessary buoyancy until the pressure in the slide becomes great enough to overcome the slide's weight and friction, thus causing the slide valve to close. 10. A hydraulic impact device according to claim 1, c h a r a c t e r i z e d in that the filling valve and the drain valve are combined to form a unit (6) wherein the valve slide (43) moves between two extreme positions (fig. 4a, fig. 4b), one of which extreme positions (fig. 4a) simultaneously opens the filling valve (51) and closes the drain valve (52a), while the other extreme position simultaneously closes the filling valve and opens the drain valve (52a), movements of the valve slide being controlled by liquid which is alternately conveyed from the high pressure chamber (32) through channels (54a,b) in the upper part of the piston rod (8) to one or the other side of the valve slide while at the same time other channels (50a,b) are opened from the opposite side of the valve slide to the low pressure chamber (33), movements of the valve slide (43) being controlled by the position of the upper part of the piston rod (8). 11. A hydraulic impact device according to claim 1, c h a r a c t e r i z e d in that the inlet valve (6, fig. 5, fig. 6) is a globe valve (57a-b, 58) which when the drop hammer is lifted so that the piston (10) is in the lower end position is closed mechanically (fig. 5b) by a projection on the piston rod's extended part (8b), that the globe valve is thereafter kept closed by the pressure difference between the high pressure reservoir (32) and the piston cylinder (34,49), that the said pressure difference, provided that the drain valve (71, 52b) is closed, is neutralized again (fig. 6a) by a small passage (75a-b) which is created by the piston rod's extended part (8c) when the piston is in the upper position, and that the removal of the said pressure difference causes a spring force (76) to rapidly open the inlet valve (57b,58) completely (fig. 6b). 12. A hydraulic impact device according to claim 11, characterized in that the small passage which neutralizes the pressure difference above the globe valve (57,58) is activated mechanically, the globe valve being in two parts (55a,57a), the pushing force from the piston's movement towards the upper end position being great enough to overcome the pressure difference on the smallest part (55a) of the globe valve, with the result that the spring force (76) thereafter opens the largest valve seat (57a) when the pressure difference is approximately neutralized. 13. A hydraulic impact device according to claim 11, characterized in that the small passage which neutralizes the pressure difference above the globe valve is created by a groove (75a) in the piston rod's extended part (8c), the groove (75a) neutralizing the sealing between the piston rod and the space (77) below the globe valve. 14. A hydraulic impact device according to claim 1, characterized in that the drain valve consists of a slide (71) which in the open position (fig.5a, fig.6a) partially closes a prechamber (77) between the filling valve (57,58) and the piston cylinder (49), and in the closed position (fig. 5b, fig.6b) opens between the said prechamber and the piston cylinder, thus causing the flow through the prechamber (77) to press the slide (71) in the drain valve (71, 52b) to the closed position when the filling valve is opened, while a spring mechanism (72) returns the slide to the open position when the filling valve closes and the flow through the prechamber ceases.

Inventors: AARDAL KAARE, REE SIGURD, AARDAL, KAARE, REE, SIGURD
Applicants: AARDAL KAARE, REE SIGURD, SELANTIC IND AS, AARDAL, KAARE, REE, SIGURD, SELANTIC INDUSTRIER A/S
Application year: 1994
Main classification: E21B49
IPC codes: B25D9, E21B25